Erosion reducer



July 15 1968 J. P. PICARD EROSION REDUCER Filed Jan. 20, 1957 FIG.|.

3,392,669 ERGSION REDUCER Jean P. Picard, Morristown, NJ., assignor tothe United States of America as represented by the Secretary of the ArmyContinuation-impart of application Ser. No. 522,796, Jan. 24, 1966. Thisapplication `Ian. 20, 1967, Ser. No. 610,698

27 Claims. (Cl. 102-38) ABSTRACT OF THE DISCLOSURE Inexpensive chemicaladditives belonging to the silicates family -have been discovered tohave the inherent ability when added to propellant systems, to reducewear or erosion of members coming in contact with hot gases resultingfrom the combustion of the propellants.

This invention is a continuation-in-part of my copending patentapplication, Ser. No. 522,796, led Jan. 24, 1966, for Erosion Reducerand assigned =to the same assignee hereof and which is now converted tostreamlined application Ser. No. 676,681.

This invention relates broadly to ordnance items and more particularlyconcerns inexpensive and readily available chemical additives which areused with propellant systems for reducing wear or erosion in members,such as gun barrels, coming in contact with hot gasesforrned by ignitionof the propellant.

The problem of excessive gun barrel wear has been a most vexing onebecause of economy and technical considerations. Jacobson et al., U.S.Patent No. 3,148,620, deals with the problem at length. However, theproblem has not been adequately solved principally due to needed furthergun barrel wear resistance and the generally high cost of additivesemployed. Etzkorn, German Patent 719,418 discusses the application oflubricating mechanisms to improve gun barrel wear by reducing frictionwhen a bullet moves through a barrel. His device requires the use ofcartridge bags having fibers of about 1 to 6 denier, the bag containingthe lubricating medium or the lubricant is embodied in the fibers of thebag. Quite obviously, his lubricating device does not lend itself tomodern production methods and is altogether too costly when consideringthe tremendous quantities of cartridges manufactured by or for theGovernment today.

It is therefore a broad object of this invention to economically reducethe wear or erosion in a member, such as weapon barrel, which issubjected to hot gases formed by ignition of propellant.

Another object of the invention is to provide cartridges witheconomically and readily available chemical additives which produce alaminar cooling layer on surfaces of members to be protected againstwear, said additives being most e'icient in reducing gun barrel wear,and smoke and flash upon ignition of propellant within the cartridge.

Further objects and advantages will become apparent to those skilled inthis art from the appended claims and following description of theinvention and exemplications thereof, made in conjunction with theaccompanying drawings showing exemplary embodiments and wherein:

FIG. 1 is a front elevation view, partly broken away, of a cartridgeembodying an additive of the present invention;

FIG. 2 is a view of an unfolded sheet utilized in the cartridge of FIG.1; and

nited States Patent O ce 3,392,669 Patented July 16, 1968 FIGS. 3 and 4are modified cartridges of FIG. 1.

Briefly, the present invention is based on my discovery that byincorporating certain inorganic additives (with cellulosic bers ifadditional strength is desired, or synthetic polyester fibers ofterephthalic acid sold under the trademark Daeron) into a propellantcontainer, such as a cartridge case, for example, that gun barrelerosion can be greatly reduced.

More specifically, I have discovered that inexpensive and readilyavailable additives, such as SiO2, MgO, or A1203, individually, or mixedin any proportions, or as SiO2/Mg0 and SiO2/Al203 occurring in nature astalc, feldspar, and kaolin characterized by the mineral kaolinite, andfurther characterized by the generic name of silicates and havingrespectively the following empirical formula 3 MgO14SiO2 H2O, K2O A12036Si02, and

if contained within a cartridge case or propellant container, whenincorporated within a suitable carrier as a hydrocarbon or plasticcomposition or within the propellants and placed inside the cartridgecase or propellant container, that gun barrel erosion is remarkablyreduced as well as smoke and ash when the cartridge case is fired. If amixture of the oxides is used, I have found that excellent results areobtained when the oxides have the following ranges:

Wt. percent Si02 45-65 MgO 20-55 SiO2 35-79 A1203 20-50 The oxides arepreferably of tine particle size ranging between about l to 60 micronsand it is not necessary that the oxides be free from ordinary impuritiescarried therewith. If the natural occurring minerals, talc, feldspar,kaolin or kaolinite are used, they may constitute the entire additive.

The oxides, individually or mixed, or talc, will be used in quantitiesvarying between about 1 to 5 weight percent of the propellant charge,depending upon the operating pressure of the weapon involved and thetype propellant being employed. The cellulose or Dacron fibers, whenused, will constitute about l to 2% of the weight of the SiO2, MgO, orA1203, lor a mixture thereof, or talc, feldspar, kaolin and kaolinite.

My additives may be dispersed in a carbonaceous carrier material such asparain or microcrystalline waxes and other hydrocarbons melting betweenabout to 400 F., or the additives may be incorporated within a suitablematrix such as plastic foam synthetic fibers, and the like. Verysatisfactory results have been obtained with polyurethane foams andparaiiin waxes, the latter having a preferred melting point betweenabout to 250 F. Optionally, the additives of the invention may be usedadvantageously without any carrier material by blending with thepropellants as will be described in detail hereinafter.

When a carrier is employed, my inventive sheet will comprise thechemical additive or additives dispersed in a carrier wax which will beimpregnated in a textile adjacent the front part of the charge.Determination of minimum sheet thickness can be readily computed fromthe formula set forth in the patent to Jacobson et al. supra:

where C is the calibre of the firearm or weapon in cms.; and cm.2 refersto the area of the sheet. By sheet, I refer to my additives,incorporated or dispersed, whether generally homogeneously or not withina wax carrier, including the textile or fabric upon which it is coatedor impregnated. When polyurethane foams are employed as the textile, myadditive will be incorporated therewithin to comprise the sheet.

The formula given above may be expressed more generally so that itapplies to all substances as follows:

30\/ gram calories per sq. cm. of sheet surfacethat is the substance issuch that in reacting with the propellant gases it absorbs 30\/ gramcalories per sq. cm. of the sheet surface.

One embodiment of my invention is illustrated in FIG. l wherein acartridge is shown having a metal case 10, propellant charge 12comprised of a suitable propellant to be hereinafter described and aprojectile 14. Within case an-d in contact with the inner surfacethereof is a textile wrap 16 which may be of any suitable material suchas rayon (preferred), cotton, silk, and the like. The upper section ofwrap 16 has a plurality of vertical slits 18 (FIG. 2) through part ofits length which form flaps 20 as shown in FIG. 1.

Textile 16 is coated, or coated and impregnated with an additive layer22 composed of powdered SiO2, powdered MgO, powdered A1203 or powderedmixtures thereof, or fel'dspar, kaolin and kaolinite. Flaps Ztl and theadditive layer coating 22 are adapted to be folded in overlapping mannerover the upper surface of propellant charge 12.

The additive coating is prepared by melting the wax and thereaftermixing with my powdered additive in proportions hereinafter described.Thereafter, the coating is applied to the fabric in the desiredthickness and permitted to cool and thus forming my sheet.

When a cartridge is prepared without a carrier material in accordancewith my invention, the SiO2, MgO, or A1203, individually, or incombination, as talc, feldspar, kaolin or kaolinite, may -be admixed orincorporated directly within propellant 12 or coated directly onto theouter surfaces thereof, the chemic-al additives in either casecomprising about l to 5 percent by weight of the propellant charge.Optionally, my additives may be enclosed or contained in small plasticcapsules 23, as shown in FIGURE 4, of cellulose acetate, for example,and dispersed throughout the propellant or the additives may be simplydropped into a cartridge case or propellant container prior to itsloading, the additives again comprising about l to 5 percent by weightof the propellant charge. Obviously, if no carrier is used, thenecessity of yemploying a fabric or plastic foam is completely obviated.

Coated fabric 16 which is preferably one-half to fivesixths the lengthof the charge, may be wrapped around the propellant 12 or it may be heldin position in the cartridge as the propellant material is poured in. IfIdesired, fabric 16 may be secured to the inner wall of the case by glueor other suitable means so as to retain the coated fabric in position.Thereafter flaps 20 are folded over and projectile 14 is placed on topof the flaps as shown in FIG. l. It will be understood that theinvention is equally applicable to cartridges other than as illustrated.For example, artillery ammunition of the fixed, semitixed, separated, orseparate-loading and high-pressure weapon types may be`usedadvantageously with the additives described.

In the modified cartridge of FIG. 3, a sponge-like polyurethane foam'24, impregnated with the additives of my invention, replaces the textile16 and layer 22 of the cartridge of FIG. 1 and will similarly beprovided with slits at its upper portion to facilitate its folding in anoverlapping manner over the upper surface of propellant charge 12. Ifdesired, the impregnated polyurethane foam material may be glued, forexample, to the inner wall of the case in a manner similar to thetextile sheet.

In preliminary testing of the effectiveness of my inexpensive yandreadily available additives, laboratory apparatus was used whichcomprises a modified closed bomb simulating gun firing. Theeffectiveness of my additives was evaluated by measuring loss in weightof perforated steel cylinders employe-d to vent the combustion productsproduced by the burning propellant and around a selected portion ofwhich was placed my sheet or impregnated polyurethane foam, or myadditives were added or admixed into the propellant directly asaforedescribed. My additives work with equal effectiveness in cartridgesland shells ranging from 22 calibre small arms ammunition to 205ammunition. The amount and thickness of my additive sheet or impregnatedpolyurethane foam when a carrier is used, will depend on the size of thecartridge or shell as aforedescribed. For example, the textile 16 for a105 mm. high explosive anti-tank shell was a piece of rayon woven fromspun viscose rayon yarn containing a durable water repellant of melamineresin base and weighed between 2.80 and 3.20 ounces per square yard. Therayon was pl-aced on a smooth surface and my additives poured thereonand spread evenly by scraping with a blade and resulted in a sheetslightly under 1/16 inch in thickness. Determination of minimum sheetthickness can be readily computed for any calibre weapon from theformula aforementioned. In the case of impregnated polyurethane foams,the identical formula for calculating sheet thickness will be used.

The propellants used in determining the effectiveness of my additive aredescribed in Table I below:

TABLE I.-PROPELLANT COMPOSITIONS AND PROPERTIES THEREOF Propellant M2 M9M30 Composition:

N itrocellulose 77. 57. 75 28. 00 (Percent N in nitroeellul0se) (13. 25)(13. 25) (12. 6 N itroglycerine 19. 40. 00 22. 50 Nitroguanidine 47.Potassium Nitrate 1.

Barium Nitrate .40

Thermochemieal Properties;

Isochorie Flame Temp., K 3,319 3 799 3, 040 Force, ft.lbs./lb 364, 000Unoxidized Carbon, percent 3. 2 Combustibles (Hg-i-CO), percent. 47. 232.8 41.0 Heat of Explosion, cal./gm 974 Gas Volume, 1noles/gm. 0.4308

To show the superiority of my additives over other known additives, anerosion study was conducted using M2 propellant wherein the fabricmaterial was a spun viscose rayon yarn covered with wax containing theadditives as aforedescribed and the polyurethane foam Ihad a density of22 pounds per cubic foot although foams ranging between about 10 to 30pounds per cubic foot have been found to work very satisfactorily.

TABLE IL EROSION STUDY Propellant type, M2. Propellant charge, 35 grams.Pressure range, 15,000 to 16,000 p.s.i.

Erosion Weight per shot Additive of expressed Additive, in mg. lossgrams in weight per shot Propellant (alone) 24.1 Parafn Wax (mp. 180 F2. 2 2.8 2. 0 0. 8 2. 0 0. 6 Kaolinite (alone) 2.0 0. 5 45 Pts.Feldspar/55 Pts. Wax 4. 0 0.7 45 Pts. Feldspar/55 Pts. of polyurethanefoam 4.0 0.8 45 Pts. AlgO3/55 Pts. wax 4. o 0. x 45 Pts. SiO2/55 Pts.Wax 4. (l l). 2 45 Pts. 'NO2/55 Pts. wax 4.0 t). 8 45 Pts. 5.5/45SiOi/AlzO/ Pts. \v 4.0 0. 7 22 Pts. 55/45 SiO2/AlgO3/78 Pts.polyurethane foam 4.0 1.5 45 Pts. 75/25 SiO2/AlgO3/55 Pts. ofwux 4.0 1.2

In Iall cases, the oxides used were of a particle size of about 1 to 60microns and the Wax had a melting point of `about 180 F., unlessotherwise indicated.

The chemical compositions of the aforementioned feldspar, kaolin andkaolinite lare presented in Table III, IV 5 @and V below:

TABLE IIL-TYPICAL CHEMICAL COMPOSITIONS OF FELDSPAR USED Samples(percent) TABLE IV.-TYPICAL CHEMICAL COMPOSITIONS OF KAOLIN USED Samples(percent) Ingredients Silica, SiOg 45. 46 47.02 46. 57 Aluminum Oxide,A1203 38. 05 37.87 37.09 25 0. 59 0. 80 0. 05 0.17 0.08 0.25 0. 20 0. 160. 24 0.14 0.24 0. 0. 27 0. 20 0. 11 1. 32 0. 21 1. 29 Loss on Ignition,H2O.. 13.82 13. 49 13. 54 Particle size in micron 1-60 1-60 1-60 30TABLE V.TYPICAL CHEMICAL COMPOSITIONS OF KAOLINITE USED Samples(percent) Ingredients 35 Silica, SiO2 46. 77 Aluminum 37.79 Fei-ricOxide, FegOg 0.45 Ferrous Oxide, FeO.. 0.11 Magnesium Oxide, Mg 0.24Calcium Oxide CaO 0.13 Potash, R20 1. 49 Soda, Na2O 0.05 Titanium O Losson Ignition, H2 12. 95 Particle size in micron 1-60 When M9 propellantwas used, the following results were obtained:

TABLE vL-EROSION STUDY Propellant Type, M9, Flake (3 mils). PropellantCharge, 42 grams. Pressure Range, 50,000 to 55,000 p.s.i.

Additive Propellant (alone) Parain Wax (M.P., 180 F.) SiOg (alone) A1203(alone) T102 (alone) 45 Pts. SiO2/55 Pts. wax.

45 Pts. 55/45 Sim/A1203 Pt 01W 22 Pts. 55/45 Sto/A120072 Pts. of polyu45 Pts. 75/25 SiOglAlzOg/ Pts. of wax 45 Pts. Feldspar/55 Pts. ofpolyurethan 45 Pts. of Kamin/55 Pts. of Wax 45 Pts. of Kaolinite/55 Pts.of wa 45 Pts. of Tale/55 Pts. of wax In all cases above, the oxides orfeldspar, kaolin, and kaolinite were of the order of about 1 to 60microns particle size.

It is also within the embodiment of my invention to add the additives bytadmixture or blending within the propellant charge. To demonstrate thesuperiority of my additives over other known additives, comparativeerosion tests were conducted using propellant compositions, fabricatedby either extrusion or ball-powder technique and having a wide range ofcomposition, ame temperature, force and heat of explosion. When theamount of additives used ranged between l to 5%, they were found to beequally etective when admixed with the propellants as when applied as allayer |around the propellant las shown in Table VII. In yall cases, theoxides used, such as talc, feldspar, kaolin and kaolinite were ofparticle size of about l to microns.

TABLE VII.COMPARATIVE EROSION STUDIES Relative Additive Coating Heat ofErosion Propellant Composition Added, Added, Explosion, (5 Shots), ForceQuiokness Percent Percent caL/gm. mg.

F. 65 F. 70 F. -65 F.

IMR 8138M (see Infra) 3. 5 896 8.0 100 100 100 109 IMR 8138M T102 2 12.8 908 1.7 98 6 97.5 112.7 112 3 IMR 8138M AIF 2 2 3.1 902 3. 7 97 498.2 108.3 108 0 IMR 8138M Tale (Montan 2 5 3.2 898 0. 8 97 5 97. 9 119.4 110 6 Ball Powder (see Infra) 1. 0 871 6. 3 100 100 100 100 BallPowder Talc (New York). 2 0 1. 0 867 0.8 97 5 97. 9 98. 2 99 0 3. 6 1,042 8. 8 91.9 94. 7 84.0 84. 0 3. 5 1, 942 1. S 91.9 93. 3 87. 4 89. 8M2 Feldspar 3.5 1, 042 3. 2 91.9 93. 4 36.2 88. 9 M2 Kao1inite 3.0 1,050 2. 1 92.0 94. 1 85. 9 87.8

2.0 979 6. 5 95. 2 94. 1 87. 3 87. 2 2. 0 969 2. 5 96. 5 96.2 89. 0 89.2 4. 0 955 6.8 87. 1 86. 1 85. 3 84. 1 3.0 966 8. 3 89.0 90.0 86. 5 86.1 2. 5 968 8. 9 90.1 91. 2 88.2 87.5 974 6. 7 100 100 109 100 M30 T1022.0 970 5.3 97. 1 96.7 96.8 87. 2 M30 Tale (Montana 2.0 970 2. 9 97. 396. 1 97. 0 94.

8 Example III 17 pounds of kaolin having an average particle size of 3microns was mixed with 0.2 pounds of Daeron fiber,

TABLE VIlL-PROPELLANT COMPOSITIONS AND PROPERTIES THEREOF Ball powder IMR 8138M Composition:

Nitroccllulose (13.15% N), percent Nitroglyecrine. Potassium Nitrate(addetl) Barium Nitrate Potassium Nitrate l)ibutylphthalateI (added)Diphenylamiue (added) Ethyl Centralite Graphite Methyl Centralite(coating) Ethylene Dimethacrylate (coa ng DibutylphthulateDiphenylaniine Additive (added) 3 0 4. 0 0.30 2 0 Graphite (glaze) 0.0.10 Tlicrmoehemical Properties:

Isochloric Flame 'Iemperature, K 2, 834 2,810 2, 590 3, 320 3, 2

Force, tt.lbs./lb 335, 800 324, S00 308, 800 3h0, 000 362, 000

lIcat of Explosion, cal./gm 871 866 781 1, 080 977 Preparation of theproducts of this invention will be more clearly understood from aconsideration of the following specic examples which are given for thepurpose of illustration and are not intended to limit the scope of thisinvention in any way.

Example I 47 grams of kaolinite having a particle size ranging between 3to 60 microns are stirred into 53 grams of melted paraffin wax having amelting point of 180 F. The resultant mixture was thoroughly mixed whilemaintaining the temperature at about 100 C. and then poured onto a pieceof spun viscose rayon yarn of melamine resin base, the rayon yarn havingbeen placed on a smooth surface. By means of a scraping blade, a uniformthickness of about 1/16 inch of additive wax was obtained. If desired,the melted additive wax mixture can readily be poured in molds ofvarying configurations.

Example II 22 parts of feldspar having a particle size ranging betweenabout 5-40 microns are stirred into 82 parts of a resin prepolymerconsisting of:

Parts Polyethylene glycol, low molecular wt. 10.5 Polyethylene glycol,high molecular wt. 6.5 Castor oil 36.48 Tolyl di-isocyanate 46.47 Acetylchloride 0.05

After thorough mixing of the additive and prepolymer, 9.5 parts of acatalyst consisting of Parts Polyethylene glycol, low molecular wt. 17.2Glycerol (2.5% H2O) 34.5

and 8.5 parts of another catalyst consisting of:

Parts Polypropylene glycol nioxdiol 46.2 Dibutyl tin di-2-ethyl hexoate1.0

are added thereinto and further thoroughly mixed, and then poured into acontainer, suitably of steel or aluminum, for example, and cured at 210F. for at least 2 hours. The resultant mass or bun" 0f impregnatedpolyurethane foam is then permitted to cool, removed from the containeror mold and sliced into sheets of desired thickness with a band saw foruse in cartridge case or, as described under Example I, may be pouredinto molds while yet in a pourable condition.

6 to 9 grams denier and about 1/2 inch long, and then thoroughly stirredinto 22 pounds of molten parain wax having a melting point of 180 F. Theresultant mixture was poured onto a spun viscose rayon cloth of melamineresin base as aforementioned to produce a uniform layer approximately1/16 inch thick. When inserted in a 105 mm. cartridge in accordance withthe invention, the cartridge being loaded with M30 propellant, theerosion on the gun barrel after tiring rounds therethrough was 0.004 onthe barrel lands and 0.000" on the barrel grooves. When the same testwas performed using identical amounts of Ti02 or CaSO4 and wax havingidentical particle sizes and melting points, the barrel lands wereeroded 0.006 and 0.01 respectively and the barrel grooves 0.000" in bothcases. Additionally, the TiO2-wax additive produced substantially moresmoke and flash than any kaolin-wax additive aforedescribed.

Example IV Propellant formulation IMR 8138M aforedescribed containingvarious a-dditives such as talc, feldspar, kaolin, kaolinite, mica, andrelated silicate materials varying from l to 5% of propellantcomposition weight were processed using the ingredients listed below ina manner hereafter described:

Parts Nitrocellulose (13.15% N) 100 Potassium sulfate (added) lDiphenylamine (added) 0.7 Solvent total 197 1 Made of diethyl ether 65parts and ethanol 35 parts.

To the dehydrated nitrocellulose (alcohol wet), screened through anS-mesh screen and then placed in a mixer, such as a sigma blade type,for example, was added 2.5 percent by weight of talc and the requiredquantity of potassium sulfate and the whole mass dry blended for tiveminutes. Then the solvent containing diphenylamine was added while themixer was still running. The mixing operation was carried out for onehour with cold water running through the mixer jacket. The propellantcomposition was then removed from the mixer and stored in a tightcontainer until time for extrusion into desired web sizes. All screensizes hereinabove and hereinafter referred to were U.S. Standard Sievetype.

Example V Propellant formulation CR7814 aforedescribed containingvarious additives such as talc, feldspar, kaolin, kaolinite and relatedmaterials belonging to the silicates family in quantities varying from 1to 5% of propellant formulation weight were processed in accordance withthe following:

Parts Nitrocellulose (13.15% N) 100 Potassium sulfate (added) 2Dibutylphthalate (added) 2 Diphenylamine (added) 1 Solvent total 1 95 1Made of diethyl ether 65 parts and ethanol 35 parts.

The dehydrated nitrocellulose, alcohol wet, was passed through an S-meshscreen and thereafter placed in a sigmablade mixer, and 2.5 percent byweight of kaolinite added thereto and the require-d quantity ofpotassium sulfate. The resultant mass was blended for five minutes. Tothis mass was added very slowly the solvent ether/ alcohol containingdibutylphthalate and the dissolved diphenylamine, the mixing beingcarried out for about one hour. During this time, the mixer was cooledby running cold water through the double-wall jacket. The mixer was thenstopped and the propellant composition removed therefrom and stored in atight container until used for extrusion into shapes and dimensionsdesired.

Example VI Propellant formulation M2 aforedescribed containing variousadditives such as talc, feldspar, kaolin, kaolinite, and the materialsin quantities varying from 1 to 5% of propellant weight were prepared bymixing the ingredients hereafter named:

1 Made of 55 parts acetone and 45 parts ethanol.

To the dehydrated (alcohol wet) nitrocellulose, screened through anS-mesh screen and placed in a sigma-blade mixer was added 3.5 percent byweight of feldspar, or any other like materials and the requiredquantities of barium and potassium nitrates, the whole mixture beingblended for about five minutes. The solution of acetone containingnitroglycerine was then slowly added thereinto while the mixer ran forabout tive minutes. The graphite and ethyl centralite were added withthe rest of the solvent and mixing was continued approximately for twohours at 112i5 F. The mix was then allowed to cool, removed from themixer and stored in a tight container to await extrusion into desiredgrain sizes.

Example VII Propellant formulation M26E1 aforedescribed containingvarious additives such as talc, feldspar, kaolin and kaolinite and thelike materials in quantities varying from 1 to 5% of the propellantweight were obtained by using the following ingredients and mixed in themanner hereafter described:

1Made of 55 parts acetone and 45 parts ethanol. To the dehydrated(alcohol wet) nitrocellulose, screened through an 8-mesh screen andplaced in a sigma-blade mixer, was added 4% by weight of kaolin or anyof the Example VIII Propellant formulation M30 aforedescribed containingvarious additives such as talc, feldspar, kaolin, kaolinite, and likematerials of the silicates family in quantities varying from 1 to 5% ofthe propellant weight, were manufactured according to the procedurehereafter described:

Parts Nitrocellulose (12.6% N) 28.0 Nitroglycerin 22.5 Nitroguanidine47.7 Ethyl centralite 1.5 Cryolite 0.3

Total 100.0

Solvent total 1 20 1 Made of 60 parts ethanol and 40 parts acetone.

To the dehydrated nitrocellulose screened through an 8- mesh screenplaced in a sigma-blade blender was added 2% of talc by weight andone-half of the quantity of nitroguanidine. These ingredients wereblended for ve minutes. Then the nitroglycerine desensitized by solutionacetone was added to the blender while runing and permitted to continuemixing for ve minutes. The remainder of the nitroguanidine and thecryolite were added and mixed for twenty additional minutes. Finally,alcohol-wet ethyl centralite and the remainder of the solvent wereadded. The mixing operation was carried out between 1l5 F. for a totalof three hours. The propellant composition was then allowed to cool,removed from the mixer and stored in a tight container until extrusiontime. The material was then extruded in the desired shapes anddimensions.

Example IX The aforedescribed ball-powder containing additives such astalc, feldspar, kaolin and kaolinite in quantities from l to 5% wereformulated according to the composition hereafter given:

Parts Nitrocellulose (13.15% N) 83.8 Nitroglycerin 9.7 Dibutylphthalate5.5 Diphenylamine 1.0

Total 100.0

The nitrocellulose, either as ground reclaimed propellants or bers, wasslurried into 250 parts of water and heated with agitation at about 69C. To this slurry under agitation was added 250 parts of ethyl acetatecontaining the diphenylamine, To this slurry was added, by dusting intothe mixer, two parts of talc. To the talc slurry was added withcontinuous agitation 0.25 parts of dispersing agent, preferablycollagen, gelatine-like animal glue although not limited thereto,previously dissolved in 250 parts of water. Then 350 parts of a 10%aqueous solution sodium sulfate was added thereto and agitationcontinued for one hour. The ethyl acetate was then removed bydistillation and the resulting ball powder then screened, washed andreslurried in water. To this was added the nitroglycerine with continuedagitation for five to six hours at 69 C.

The above operation was followed by the addition of the dibutylphthalatedispersed in parts of water as deterrent coating. The ball powdercomposition was then removed by decantation, cooled, rolled, dried,glazed and stored into adequate containers.

The cost of my additives, i.e., Si02, MgO, A1203 or feldspar, kaolin andkaolinite does not exceed about cents a pound and is considerably moreinexpensive than other prior art additives.

Although my impregnated polyurethane foam materials are not as effectiveas the kaolinwax, feldspar-wax, and SiO3/Al203-wax sheet, it is believedthat the results obtained still indicate its high degree ofsatsfactoriness in reducing gun barrel erosion.

It is apparent from the foregoing description that I have providedadditives for use in propellant systems wherein members coming incontact with hot gases produced by ignition of the propellant areprotected against wear and erosion by the formation of cooler layers ofgas adjacent the member. Plastic and fiberglass members as well asfiberglass-metal members also benefit from the additives of theinvention. My additives are characterized by inexpensiveness and theirhigh adsorptivity for hydrocarbons and certain organic compounds whichlend themselves admirably for admixing into waxes and polyurethanes. Myadditives are further characterized by their complete compatibility withpropellant ingredients and their ability to be admixed directly into thepropellants in those instances where the size of the cartridge casesmakes it impractical to use it in a wax layer around the propellants.Further, the stability and ballistic performance of weapons employing myadditives are not at all adversely affected and they perform equallywell when placed around the propellant charge or admixed within thepropellant compositions.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

Reference is hereby made to patent application Ser. No. 523,015, ofDaniel Katz, for Wear Reduction Additives, filed Jan. 24, 1966, nowPatent No. 3,362,328, assigned to the same assignee of this patentapplication.

I claim:

1. In a propellant system for providing thrust whereby hot gases areproduced upon ignition of propellant and including means `for containingsaid propellant, the combination therewith of the improvement forreducing erosion of members coming in Contact with said hot gases, saidimprovement comprising an additive selected from the group consisting offeldspar, kaolin, and kaolinite incorporated within said containingmeans, said additive comprising 1 to 5 weight percent of saidpropellant.

2. The system of claim 1 further characterized by said additive beingadmixed with said propellant.

3. The system of claim 1 further characterized by said additive beingcoated on exterior surfaces of said propellant,

4. The system of claim 1 further characterized by said additive beingdisposed adjacent a base end portion of said containing means.

5. The system of claim 1 further characterized by said additive beingincorporated within said propellant.

6. In a system having a projectile associated with a cartridge having apropellant and means for containing said propellant, the combinationtherewith of the improvement for reducing erosion of members coming inContact with hot gases produced upon ignition of said propellant, saidimprovement comprising an additive within said containing means selectedfrom the group consisting of feldspar, kaolin and kaolinite, andmixtures of the foregoing.

7. A cartridge as described in claim 6 wherein said additive comprisesabout 1 to 5 weight percent of the propellant, said additive beingadmixed with said propellaut.

8. A cartridge as described in claim 6 wherein said additive comprisesabout 1 to 5 weight percent of the propellant, said additive beingcoated on exterior surfaces of said propellant.

9. A cartridge as described in claim 6 wherein said additive comprisesabout 1 to 5 weight percent of the propellant, said additive beingdisposed on a bottom portion of said cartridge case.

10. A ca-rtridge as described in claim 6 wherein said additive comprisesabout 1 to 5 weight percent of the propellant, said additive beingincorporated within the propellant.

11. In a system having a projectile associated with a cartridge having apropellant charge and means for containing said propellant charge, thecombination therewith of the improvement for reducing erosion of memberscoming in contact with hot gases produced upon ignition of saidpropellant charge, said improvement comprising a sheet surrounding atleast an upper half of said propellant, said sheet comprising a perviousmaterial impregnated with a chemical additive selected from the groupconsisting of feldspa-r, kaolin and kaolinite, and mixtures of theforegoing.

12. In a system having a projectile associated with a cartridge having apropellant charge and means for containing said propellant charge, thecombination therewith of the improvement for reducing erosion of memberscoming in contact with hot gases produced upon ignition of saidpropellant charge, said improvement comprising a sheet of a pervioustextile fabric impregnated with a dispersion of a carrier and a materialselected from the group consisting of feldspar, kaolin, and kaolinite,and mixtures of the foregoing.

13. The cartridge of claim 12 wherein said carrier is hydrocarbon.

14. The cartridge of `claim 13 wherein said hydrocarbon is characterizedby a melting point between about 70-400" F.

15. The cartridge of claim 12 where said carrier is paraffin wax.

16. The cartridge of claim 12 further characterized by said materialconsisting essentially of feldspar.

17. The cartridge of claim 12 further characterized by said materialconsisting of kaolin.

18. The cartridge of claim 12 further characterized by said materialconsisting essentially or kaolinite.

19. The cartridge of claim 12 further characterized by said materialhaving a particle size range of about 1 to 60 microns.

20. In a system having a projectile associated with a cartridge having apropellant charge and means for containing said propellant charge, thecombination therewith of the improvement for reducingw erosion ofmembers coming in contact with hot gases produced upon ignition of saidpropellant charge, said improvement comprising a sheet of a pervioustextile fabric impregnated with a dispersion of a carrier and a materialselected from the group consisting of A1203, a mixture of SiO2 andA1203, feldspar, kaolin and kaolinite, and mixtures ofthe foregoing,wherein cellulose fibers are incorporated within said dispersion.

21. The cartridge of claim 20` further characterized by said cellulosefibers constituting about 1 to 2 weight percent of said material.

22. The cartridge of claim 20 further characterized by said cellulosefibers being about 6 to 9 grams denier and about 1/2 inch long.

23. In a system having a projectile associated with a cartridge having apropellent charge and means for containing said propellant charge, thecombination therewith of the improvement for reducing erosion of memberscoming in contact with hot gases produced upon ignition of saidpropellant charge, said improvement comprising a sheet of a pervioustextile fabric impregnated with a dispersion of a carrier and a materialselected from the group consisting of A1203, a mixture of SiO2 andA1203,

13 feidspa-r, kaolin and kaolinite, and mixtures of the foregoing, andwherein synthetic polyester ibers of terephthalic acid are incorporatedwithin said dispersion.

24. The cartridge of claim 23 further characterized by said syntheticpolyester bers of terephthalic acid constituting about 1 to 2 weightpercent of said material.

25. The cartridge of claim 23 further characterized by said syntheticpolyester ibers of terephth'alic acid being about 6 to 9 grams denierand about 1/2 inch long.

26. In a propellant system for providing thrust Whereby hot gases areproduced upon ignition of propellant and including means for containingsaid propellant, the combination therewith of the improvement forreducing erosion of members coming in contact with said hot gases, saidimprovement comprising Ian additive selected from the group consistingof A1203, a combination of SiO2 and A1203, feldspar, kaolin, andkaolinite incorporated within said containing means, said additivecomprising 1 to 5 weight percent of the weight of said propellant, saidadditive being encapsulated in plastic and dispersed throughout saidpropellant.

27. In a system having a projectile associated with a cartridge having apropellant and means for containing said propellant, the combinationtherewith of the improvement for reducing erosion of members coming incontact with hot gases produced upon ignition of said propellant, saidimprovement comprising an additive within said containing means selectedfrom the group consisting of A1203, -a combination of SiO2 and A1203,feldspar, kaolin and kaolinite, and mixtures of the foregoing, saidadditive comprising `about 1 to 5 weight percent of the propellant, saidadditive being encapsulated in plastic and dispersed throughout saidpropellant.

References Cited UNITED STATES PATENTS 3,148,620 9/1964 Jacobsen et al102-38 3,204,588 9/1965 Jacobsen et al 102-38 3,209,689 10/ 1965McLennan 102-38 ROBERT F. STAHL, Prz'mary Examiner.

BENJAMIN A, BORCHELT, Examiner.

